ABSTRACT
OBJECTIVE To investigate the regulatory effects of couplet medicinals of Atractylodes macrocephala-Aucklandia lappa on gut microbiota and short-chain fatty acids （SCFAs） in the diarrhea-type irritable bowel syndrome （IBS-D） rats with spleen deficiency. METHODS The IBS-D rat model with spleen deficiency was induced by intragastric administration of Senna alexandrina combined with restraint stimulation. The model rats were divided into model group， positive control group （pinaverium bromide 1.5 mg/kg）， A. macrocephala-A. lappa low-dose， medium-dose and high-dose groups （0.7， 1.4， 2.8 g/kg）， with 6 rats in each group. Another 6 healthy rats were taken as the blank control group. The blank control group and the model group were given normal saline intragastrically， and other groups were given relevant drug liquid intragastrically， once a day， for consecutive 14 days. The general characteristics of rats and fecal water content were observed， and intestinal sensitivity [evaluating by abdominal wall withdrawal reflex （AWR） threshold] and the intestinal propulsion rate were determined. The serum levels of 5- hydroxytryptamine（5-HT）and SP were detected， and the pathological changes of colon tissue were observed； the protein expressions of 5-HT-3 receptor（5-HT3R）， 5-HT4R and 5-HT transporter（SERT） in colon tissue of rats were detected. 16S rRNA sequencing was performed for the feces of rats in blank control group， model group and A. macrocephala-A. lappa high-dose group； the contents of acetic acid， propionic acid and butyric acid in the feces of the rats were determined. RESULTS Compared with the model group， the body weight after 7 and 14 days of medication， fecal water content， AWR threshold， and the protein expressions of 5-HT4R and SERT in colon tissue were increased significantly in the A. macrocephala-A. lappa medium-dose and high-dose groups （P＜0.05 or P＜0.01）； serum contents of 5-HT and SP， intestinal propulsion rate （except for A. macrocephala-A. lappa medium-dose group）， the protein expression of 5-HT3R in colon tissue were decreased significantly （P＜0.01）； diarrhea relief， mental state recovery， and partially recovery of the structure of colon tissue were all found； moreover， the diversity and species number of gut microbiota were reduced in A. macrocephala-A. lappa high-dose group and the content of butyric acid in fecal samples was significantly reduced （P＜0.05）. CONCLUSIONS The compatibility of A. macrocephala and A. lappa can improve intestinal motility and sensitivity of IBS-D model rats with spleen deficiency， and alleviate diarrhea. This may be related to improving changes in intestinal microbiota structure， reducing 5-HT expression and butyric acid content， and increasing 5-HT4R and SERT expression.